The mole and the Avogadro constant — practice question

What concentration does a solution have if it contains $25.0\ \text{g}$ NaOH in $500\ \text{cm}^3$ of water?

• A$0.125\ \text{mol dm}^{-3}$
• B$0.800\ \text{mol dm}^{-3}$
• C$1.25\ \text{mol dm}^{-3}$
• D$3.20\ \text{mol dm}^{-3}$